Contact roll construction



Feb. 15, 1955 R. J. STOCK ETAL 2,702,320

CONTACT ROLL CONSTRUCTION Filed April 10, 1950 2 SheetsSheet l INVENTORSRobert J. .Sfock John Mc Lay 25, 5. m F Of? Green, M: Call/stare Mil/erTHE IR ATTORNE Y5 2 Sheets-Sheet 2 R. J. STOCK ET AL CONTACT ROLLCONSTRUCTION INVENTORS Robert J. Stock John Mc Loy 3 5 aim-12.,

THE/R ATTORNEYS Feb. 15, 1955 Filed April 10, 1950 F 0/? Green, MaCall/star 8 Miller United States Patent CDNTACT ROLL CONSTRUCTION RobertJ. tuck, Aspinwall, and John McLay, Leechburg, Pm, assignors toAllegheny Ludlum Steel Corporation, Brackenri-dge, Pa., a corporation ofPennsylvania Application April 10, 1950, Serial No. 155,056

3 Claims. (Cl. 1911) This invention pertains to a new and improvedcontact roll construction for electrolytic treatment apparatus andparticularly, for continuous treatment of strip metal wherein animproved distribution of current flow is obtained.

One phase of the invention relates to an improved contact rollconstruction and utilization for electrolytic treatment of strip metaland another phase relates to a construction for providing a moreefiicient and effective current flow in an electrolytic treatingapparatus and particularly, in an electrolytic plating apparatus.

In the electrolytic plating of strip metal, such as strip steel, one ormore continuous lengths of the material may be drawn from pay-ofi reels,through a wiper, an anodic cleaning tank, a rinse spray and scrubber, anacid pickling tank, a rinse spray and scrubber, a strike tank, a platingtank, rinse and spray tanks, a dryer, a powdering apparatus, a pullingunit, and finally to coiling reels. In one or more of these steps, thestock material may be subjected to electrolytic treatment. For example,in the copper plating of steel strip, an electrolytic strike tank and aplating tank require the application of current to the strip to producethe requisite flow for providing, in the case of the strike tank, apreliminary light copper plate or coating in a cyanide bath and in thecase of the plating tank, a higher current for the full application ofthe copper to the requisite thickness on the surface of the material.

In plating line as well as in electrolytic cleaning line,

it has been customary to use contact rolls which serve as v a conduct ngmeans for current flow between the strip and an anode or cathode.Considerable difficulty has been encountered in providing electricalconnections to the contact rolls for supplying current to the stripmaterial. Heretofore, it has been customary in a pull or tension line toemploy hollow or cylindrical rolls provided with steel end hubs and endshaft portions extending therefrom to which branches of acurrent-conducting bus bar are connected adjacent roll end bearings tosupply current to opposite longitudinal ends of the rolls. Due to therotation of the rolls, means must be provided for insuring efficientslip contacts between the opposite shaft portions and the bus barbranches. Due to the fact that roll shaft portions carry the current,care must be taken to avoid flash-over damage to the bearings.

The strip must make a tight contact with the rolls to prevent burning ofthe strip and this places an additional mechanical stress on the rolls.As a result, it has been customary to make the end connections to therolls through steel hub portions, rather than through bronze or copperportions which are more efiicient from a cur-v rent-conductingstandpoint. Our investigations have indicated that a contact rollprovided with end electrical connections has a poor efficiency andprovides a nonuniform electrolytic action transversely across the widthof one strip or across one strip as compared to another, where a numberof strips are carried by the same roll. We have determined that theefiiciency of the electrolytic action decreases from the ends of thecontact roll towards its center.

In todays operations, it is vital to obtain very thin coatings in aplating operation or to remove thin coatings in a cleaning operation tokeep costs down and to avoid waste of the material involved.Requirements as to coating thicknesses are at the present time ratherrigid 2,702,320 Patented Feb. 15, 1955 ICC and variations between aseries of strips being carried, or along the width of a single strip,gives rise to expensive IGJGCiS.

In copper coating steel strips, for example, we have found that thevariation in coating thickness may be from .196 to .220 across the widthof the strip or strips being plated. Supplying six volts at thegenerators, the voltage drop in the bus bars and the roll has beenapproximately 2.5 to 3.5 volts, iving an efiective contact voltage atthe roll of about 3.5 to 2.5 volts. Such a voltage drop (about 50%)heats up the roll and the bus bar branches and increases wear and tearonthe slip connections to the roll. In fact, the heat becomes so greatthat it has been customary to hose the bus bars down from time to timewith cold water. The poor electrical characteristics of such aconstruction have also necessitated slowing down the line, so that atleast a minimum thickness of coating can be obtained.

in investigating this matter, we found that direct current tends to hugthe ends of the contact roll and as a result, a strip located centrallyon the roll receives a much lighter coating or treatment than a striplocated adjacent an end thereof. There does not appear to be a good flowof current from the ends of a roll towards its intermediate portion andfurther dithculty is encountered by reason of the two end connections.That is, one end connection may be more eflicient than another or mayoifer less resistance to current flow than another and stray currentswill flow therebetween, thus setting up an additional voltage drop andfurther heating the rolls and the bus bar connections.

it has thus been an object of our invention to provide a new andimproved contact roll construction for electrolytically treating metalmaterial such as strip;

A further object has been to provide a contact roll construction that ismore effective in conducting electric current to a metal strip beingelectrolytically treated;

A still further object has been to provide a new and improved form ofcontact roll construction and connections thereto;

These and many other objects of our invention will appear to thoseskilled in the art from the following description and the illustratedembodiments thereof.

in the drawings Figure l is a vertical section taken longitudinally ofan electrolytic striking bath employing contact rolls of our invention;

Figure 2 is an enlarged end sectional view in elevation through acontact roll of our construction and taken along the line llll of Figure1;

Figure 3 is a fragmental view in elevation taken from the right end ofFigure 2 along the line IIII1I thereof;

Figure 4 is an enlarged sectional detail of springpressed, slip contactbrushes.

We have been able to solve the problems heretofore presented andparticularly, the problem as to contact roll connections by providing acontact roll to which an electrical connection is made centrallythereof, intermediate its ends, and through non-ferrous, highlyconductive material. This also overcomes previous limitations in therate of movement, or the effective rate of electrolytic treating whichmay be successfully employed for the strip material. It makes possible asubstantially uniform transverse distribution of treating action alongthe width of the material during its longitudinal movement, a minimizedvoltage drop, and avoids excessive heating of the bus bars, the roll,and other current conducting portions. It makes possible an eliminationof flash-over to roll bearings.

By using the improved contact roll construction of the presentinvention, we have cut the voltage drop down to about one volt(utilizing a six volt source), have eliminated dangerous or appreciableheating, and have minimized wear and tear on the bus bars and the otherparts. We provide a direct, highly conductive, non-ferrous con nectionto the contact roll, since the connections no longer have to be madethrough ferrous metal to provide the requisite mechanical strength. Weget a new and improved current flow distribution along the length of acontact roll which is from the center of the roll towards its end. Suchfiow is enhanced by the normal tendency of the current to concentrate atthe ends of a Contact roll. By using a single contact with the roll, weavoid stray currents that are set up by counter-voltages, and enhanceand improve the effective flow of current along the length ofthe contactroll.

In a contactroll of our construction, the maximum variation in the depthof a plated coating produced on the material along a roll of about 6 ft.in length is now about .196 to .195; this is about half the minimumvariation of about .1-96 to .220 that is possible using a con ventionalroll construction. Coil runs of about 45 to 50 tons can now be easilyeffected in a 24 hour period as compared to a previous maximum of about27 to 30 tons, using a tank width of about 60 inches. in addition,cooling means for the bus bars is no longer necessary.

In the illustrated embodiment of our invention, we have. shown contact.rolls in a plating line each of which is supported by end closures orhubs of ferrous metal. Bach roll has a non-ferrous or copper contact hubor ring positioned centrally or intermediate its ends which is brazed orsoldered thereto and has a non-ferrous shaft or bar extending throughone of the end hubs, past its end bearing to carry a non-ferrous metalcommutator or cylindrical contact wheel. A bus bar from the generator isconnected to a bus bar squirrel cage which supports spring-loadedbrushes that ride on the cylindrical surface of the commutator orcontact wheel.

For the purpose of illustrating our invention, we have shown equipmentwhich is connected for effecting a plating operation, such as forapplying a copper coating to steel strip. The strip may be a singlewidth strip corresponding to the width of the contact rolls or, as ismore customary, may be a series of narrow-width strips positioned in atransversely spaced-apart relationship on the contact rolls and drawnfrom coils in line through treating apparatus and when the treatment isfinished, recoiled at the other end of the line.

Our invention relates particularly to a new and im proved form ofcontact roll construction. To illustrate a use of our roll construction,we have shown apparatus employed in an electrolytic striking (see Figure1).

Referring to Figure l, a strip 1%) is carried over a contact roll atposition A. The roll 11 is shown positioned with its lower portionextending slightly into a water tray 12 to keep it moist. The strip issupplied with current of negative potential by the contact rolls 11 atpositions A and B that represent opposite longitudinal. ends of astriking bath metal container 16 and is guided substantiallylongitudinally therethrough by a pair of end-mounted, submerged guiderolls 13. The container 16 may be filled with a suitable strikingliquid, such as copper cyanide, and has an inner, non-conductive coatingor layer 17, such as of a rubber that is resistant to the. bath liquid.The container 16 is mounted on longitudinal and transverse beam members14 and 15 and carries an electrode metal catch and support tray 19. Thetray 19 rests upon wood or other insulating cross members 18 to space itand position it with respect to the bottom of the container 16. A pairof vertical upright pieces 25 are secured to side flanges of the tray 19at opposite longitudinal ends thereof and are secured. to a pair .oflongitudinally-extending bus bars 26 to form an electrode frameconstruction. A series of cross rods 27 are secured in a spaced-apartrelationship along the bus bars 26 and serve as hanger bars for aplurality of removable electrode books 28.

As shown particularly in Figure l, electrodes 29 are adapted to restinthe lower portions of the hooks 23 and to be supplied with positivecurrent where the bath is used for a preliminary or striking platingoperation. The tray 19 has a protective, non-conductive, inner coating17 and serves to catch any electrode material falling away from thebooks 28 and to support scrap electrode material therein. In thismanner, electrode material is positioned on opposite sides of the strip10 as it moves through the bath container 16.

In Figures 2 and 3, we have shown details of the con- Struction of ournew form of contact roll. This roll has a cylindrical portion 57,preferably of a ferrous metal suchas steel; a non-ferrous. highlyconductive connector hub 58 is securely positioned within its boreintermediate its ends. The bore of the cylinder 57' is planed ormachined out at 57b to permit the insertion of the hub 58 from, theright hand. end of the roll and the seating of it within an offset boreportion 57a. When the hub 58 has been positioned as shown in Figure 2and the ends of the roll cylinder 57' are still open, the cylinder ispositioned to stand on its left hand end, and a highly conductivesoldering material, such as Silfoss, is poured in along an end groove58a to flow downwardly between the flange portion of the hub and thebored-out seat 57a of the cylinder. The solder builds up at 59a toprovide a strong, but highly electrically eflicient metal-to-metalcontact between the hub 58 and the internal bore 57a of the cylinder57'. The cylinder 57 maybe heated to effect this operation.

The hub 58 has an internal bore which receives a reduced end portion 60aof a conductor bar or shaft 60. The conductor shaft 60 is mounted withinthe bore of the hub 58 preliminary to. the insertion of the hub withinthe cylinder 57 in substantially the same manner as outlined insecurely-electrically connecting the hub to the cylinder. The conductorshaft or bar 60 is also of non-ferrous, highly conductive metalconstruction. After the hub 58 has been secured with its shaft 60 in theposition shown in Figure 13, end or closure hubs 61 and 61' may then bemounted in position within the cylinder. As shown, the end hub 61 is ofsimilar construction to the end hub 61', except that the latter has aslightly different size bore. Thus, a description of the end closure 61will suflice. The hubs 61 and 61' are of ferrous metal such as steel toprovide requisite mechanical strength for the roll construction. A stripline is ordinarily drawn under high tension over a series of rollsincluding contact rolls during its processing. Thus, friction must beminimized and such rolls must have a high mechanical strength towithstand the forces involved.

The end closure or hub 61 (61) has a circular front flange and awelded-on (see weld 62a) circular back flange 62 which are adapted toslide Within an enlarged bore seat portion 570 of the cylinder 57 and tobe secured thereto by weld metal 61a. The right hand closure hub 61 issecurely feathered or mounted and inset on a portion 63a of a steelsleeve shaft 63 which extends outwar ly along the conductor shaft 66 ina spaced-apart rela tionship with respect thereto. The sleeve shaft 63extends through a suitable bearing unit, such as a lones- Timken pillowblock box or unit 64 and at its outer end portion 630 carries a circularsupport flange 65 securely inset thereon. The flange 65 is of annularshape and is adapted to carry an electrical contact wheel or commutator68. The sleeve shaft 63 is adapted to rotate with the conductor bar orshaft 60, but is segregated and held in an electrically, non-conductingrelationship with respect thereto by: insulating circular end pieces 64athat are mounted within inset bore portions 6312 at its opposite ends.The pieces 64a may be of Micarta or other suitable insulating materialand extend about the conductor shaft 60..

A cone-shaped wedge member 69 has a cylindrical internal bore which isadapted to rest upon and make good electrical contact. with theconductor shaft 60 at its outer end. The wedge member 69 has an outertapered or conelilce periphery whichv cooperates with a similar boreperiphery 68a of the contact wheel 68 andis mounted thereon byadjustable bolts 70, so that the tightness of fit between the wheel 68and the shaft 60 can be adjusted as desired. The wheel 68 and the wedgemember 69 are both of non-ferrous, highly conductive metal and theformer has an outer periphery of planar-cylindrical shape to serve as asurface for spring-pressed slip or slide contact brushes 71. The wheelor commutator 68 is secured to the support flange 65- by bolts 67 whichare mounted insulating sleeves 66 and on insulating washers to preventcurrent from flowing from the wheel 68 to the sleeve shaft 63 and thus,to the bearing box or unit 6d within which it is journaled.

In Figure 4, we have shown an enlarged sectional detail ofspring-pressed contact brushes 71 such as employed in motors andgenerators which may be used in this connection and which are carried bya series of backwardlyprojecting mountingv bracket arms or members 72. AU-shaped, upright member or end bracket 74 that is positioned oninsulation 75 and is secured by bolts 75a through insulating sleeves andwashers to a base member 76. The base member 76 is welded to extend froma supporting I beam 77. Electrical bus straps 81 are at their upper endssecured asby soldering, or brazing to the front end of a non-ferrous.stud 79 that extends forwardly from a back wall portion 74a of thebracket 74. Bus

straps 80 of U-shape are also secured to the front end of the stud 79and extend backwardly therefrom. The back or inner ends of the straps 80are secured by bolt and nut assemblies 73 between the mounting brackets72 and the back wall portion 74a of the bracket 74 to supply current bya plurality of short paths to the brushes 71. As shown particularly inFigure 3, the conductor straps 80 are formed into somewhat of a squirrelcage arrangement and connect directly at their ends to the sixbrush-mounting brackets 72. Since all of the members from the bus barstraps 81 to the hub 58 are of non-ferrous, highly conductive metal,such as copper, bronze, etc, it will be apparent that a highlyefiicient, low resistance path is provided for current flow from the busstraps 81 to the intermediate portion of the roll 11 to which electricalconnection is made. It will also be apparent that no current flowsdirectly through the sleeve shaft 63, the bearing units 64, or throughthe closure hubs 61 and 61' from the bus bar straps 81.

The closure hub 61' at the other end of the roll 11 is secured on a studshaft 85 that is carried by a pillow bearing unit 64. It will be notedthat a splash member 78 is positioned beneath each bearing unit 64 andthat each unit is mounted on the upper flange of the I beams 77 throughinsulation pieces 75. In the case of the left hand unit 64, a metalspacer member 84 is provided.

Ordinarily, about six volts is sufiicient and it will give an effectiveplating voltage at the contact roll surface of about five volts. Thestarting amperage may be about 20,000 total with the intermediate rollscarrying about 5,000 amps. each and the end roll pairs carrying about6,000 amps. each.

Previous to our invention, the width of strip which could be effectivelytreated was limited. For example. in a plating operation a poor coatingwas obtained with a width a strip of 18 inches and this constituted theabsolute maximum width dimension. Now, employing our invention, an 18,20, or wider inch strip can be substantially uniformly coated in aneffective manner without any difficulty. In accordance with ourinvention, we provide an intermediate connection to each contact roll 11through non-ferrous parts. Furthermore, the tendency of direct currentto hug the ends of the rolls is utilized in obtaining an efficient flowof current towards such ends Without the counter-flow currents incidentto the previ' ous method of connecting each roll end to the supply ofcurrent. This is a problem which has been long outstanding in the artand on which many millions of dollars have been spent by others in anattempt to solve it.

What we claim is:

1. An improved contact roll construction which comprises, a hollowcylindrical contact roll of ferrous metal having a good mechanicalstrength, a pair of strong ferrous metal end hubs secured withinopposite end portions of said roll for rotation therewith, a strongferrous metal end shaft extending outwardly from each of said hubs andsecured thereto for rotation with said hubs and said contact roll,external bearings at each end of said contact roll rotatably mountingsaid end shafts, one of said end shafts being a sleeve shaft having anopen end bore therealong, an electrically-conductive non-ferrous metalconnector hub positioned centrally within said contact roll intermediateits ends and having its outer peripheral surface secured to and in aneflicient electrical conducting relationship with an inner peripheralsurface of said roll for rotation therewith and providing an exclusiveelectrical current connection with said roll, an electrically conductivenon'ferrous conductor bar positioned in a peripherally spaced relationwithin and along the bore of said sleeve shaft and having inner andouter end portions extending longitudinally through opposite ends ofsaid sleeve shaft, annular insulating pieces set within the bore of saidsleeve shaft in engagement with said conductor bar to hold it in asubstantially centrally-aligned spaced and and non-conductingrelationship with the bore of said sleeve shaft, the inner end portionof said conductor bar being secured within said connector hub in aneificient electrical conducting relationship therewith, and electricalcontact means of non-ferrous metal construction securely mounted on theouter end portion of said conductor bar and secured through insulatingmeans to the outer end portion of said sleeve shaft for rotationtherewith.

2. An improved contact roll construction as defined in claim 1, whereinsaid contact means comprises an electrically conductive non-ferrousmetal contact wheel mounted in adjustable-wedging andelectrically-conductive engagement on the outer end portion of saidconductor bar, and wherein a mounting means for said contact wheelcomprises a support secured on the outer end portion of said sleeveshaft and adjustably secured through said insulating means to saidcontact wheel.

3. An improved contact roll construction which comprises, a cylindricalcontact roll of strong ferrous metal construction, a pair of strongferrous metal end hubs secured within and closing off opposite ends ofsaid contact roll and having separate strong ferrous metal shaftportions extending outwardly therefrom, bearings at each end of saidroll rotatably mounting said shaft portions, an electrically-conductivenon-ferrous metal connector hub secured centrally within said rollintermediate its ends and providing an exclusive electrical conductingpath thereto, a highly conductive non-ferrous metal conductor barextending through one of said shaft portions into said connector hub andbeing secured in an efficient electrically-contacting relation thereto,said conductor bar extending outwardly through said one shaft portion ina pcripherally spaced-apart relationship with respect thereto,insulating means positioned between said conductor bar and said shaftportion adjacent opposite ends of said shaft portion, anelectrically-conductive non-ferrous contact wheel about an outer end ofsaid conductor bar, an electrically-conductive wedge-shaped sleevemounting said contact wheel on said conductor bar and having means toadjust said sleeve axially along said contact wheel, a ferrous metalmounting fiange secured to and projecting from an outer end of said oneshaft portion, and means securing said mounting flange to andelectrically insulating said flange from said contact wheel.

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